Roof supports



A. W. DUNCAN ROOF SUPPORTS May 26, 1959 2 Sheets -Sheet l Filed May 18, 1953 F/GJ.

lob

Attorney y 1959 A. w. DUNCAN 2,888,231

' ROOF SUPPORTS Filed May 18, 1953 2 Sheets-Sheet 2 IOb POSITION 0 POSITION b 325.5. I E=5-E- POSITION C POSITION d POSITION e INVENTOR.

ANGUS W. DUNC United States Patent ROOF SUPPORTS Angus Wellesley Duncan, Worcester, England, assignor to The Mining Engineering Company Limited, Worcester, England Application May 18, 1953, Serial No. 355,831 Claims priority, application Great Britain May 27, 1952 6 Claims. (Cl. 248-356) Roof supports used in underground mining practice are commonly of the yielding type. The yielding feature may take the form of friction controlled sliding of the constituent members of the supports, and the crushing of timber forming part of the support, or the opening of, a valve in a hydraulic system at a predetermined pressure. Roof supports of this type may be props or chocks which are tightened initially between the floor and roof by. means of manually driven wedges, manually operated hydraulic pumps or power operated pumps or rams. Such roof supports are commonly moved forward as each web 'of the seam is completed.

. Whilst the roof is supported in this way, it subsides gradually and exerts on the supports considerable pressure which may be of the order of tons on a normal prop. The extent of the subsidence is usuallyquite large (of the order of 6 inches) during the period (say both.

It is an object of the present invention to provide a method and apparatus by which at least a proportion of this energy is made available for doing useful work in the operation of the mine. i

From one aspect, the invention provides for the storage of energy derived from the pressure on a support supporting a mine roof due to the subsidence of the roof for the later release of such energy under controlled conditions to do useful work in the mine.

From another aspect, in accordance with the invention, the subsidence of the roof against the resistance of a roof support is caused to charge an energy storing device 1 (such as a hydraulic accumulator) from which the energy is withdrawn as required for the performance of useful work.

From yet another aspect, the invention provides a roof support including a hydraulic ram which is connected to a hydraulic accumulator, the system being provided with valves which limit the pressure in the system and with means whereby energy stored in the accumulator can be caused to do useful work. Such useful work may, for example, be to give a high initial pressure on the roof at'the next setting of the support or to move the support (or another support) into a new position' in the mine.

Patented May 26, 195? accumulator connectable for charging from the main cylinder under roof load, connectable to an auxiliary cylinder within the main cylinder to exert pressure upon a piston therein and thus upon a piston interconnected to the piston in the auxiliary cylinder and working in the reservoir to place pressure upon the fluid in the reservoir and thus to transfer it to the main cylinder for the setting of the prop, and connectable to the main cylinder once the prop is set to exert a preloading pressure to the ram. r

The various connections of the hydraulic accumulator may be made through a manually operable valve and the transfer of fluid from the reservoir to the main cylinder may be made through a tubular connecting rod joining the piston in the reservoir to the piston in the auxiliary cylinder.

Further in a preferred form of the invention, provi-. sion is made for the connection of an external pressure line to the reservoir above the piston therein for initial setting of the prop.

Other parts of the invention are embodied in the preferred forms which will now be described in some detail by way of example, with reference to the accompanying diagrammatic drawings in which:

Fig. lis a section of one form of prop embodying the invention;

Fig. 2 is a section of another form of prop;

Figs. 3 and 4 are part sections of the prop shown in Fig. 1 illustrating the valve during different stages of operation, and

Figs. 5 to 7 are part sections of the prop shown in Fig. 2 showing the valve during different stages ofoperation, only the parts immediately adjacent the valve being shown and only the passages actually in use at each state being shown.

In the form shownin Figure l, the roof support is in the form of a prop, comprising a cylinder 1 in which slides a ram 2. This ram forms a reservoir for oil or other operating fluid. A control valve 3 connects the cylinder 1 to the reservoir and limits the hydraulic pressure in the system to a predetermined amount.

Housed in the ram 2 is an hydraulic accumulator which may be of any known type but as shown comprises a piston 4 slidable in a bore 5 in the ram. This piston is recessed at its top to form with the head of the ram 2 a chamber 6 in which a spring (which may be 'air) for loading the piston is compressed.

The underside of the piston 4 may be connected to the cylinder by a rotary manually operated valve 7.. The valve 7 includes body 7a rotatable in a casing 7b pro vided with upper and lower wall components 7c and 7d.

" The upper wall 70 is formed with port 9 and the lower wall 7d formed with spaced ports 10a and 10b. The valve body 7a is provided with a bore or passage 8 extending vertically therethrough and a horizontally extending bore or passage 11 having perpendicular branches 11a and 11b.

-' In a preferred form, the invention is embodied in a )1 nectcd by a'relief valve, and fitted with a hydraulic I In one positionv of the valve body 7a, or position a, the bore 8 is in registry with the port 9 which leads to the bore 5 of the ram and with a tube 10 passing through the ram 2 and communicating at its lower end with the cylinder 1. I I In a second posistion of the valve body 7a, or positio b, the cylinder 1 is connected to the reservoir of the ram 2 via the tube 10, passage 11, branches 11a and 11b and port 10b of the casing 712.

Assume the prop is extended and supporting the roof, and the manually operated valve 7 is set to connect the cylinder 1 to the accumulator 4-5. As the roof weight is taken by the support, the pressure in the hydraulic system rises (including the accumulator) and remains at or near the pressure set by the control valve 3. When it asseasr is desired to move the support into a new position, the accumulator valve 7 is closed and the pressure in the cylinder released into the reservoir. The support is then withdrawn and re-set in its new position and tightened between floor and roof by known means, such as a manually operated pump 13, which supplies fluid from the reservoir to the cylinder. Thereafter the accumulator valve 7 is opened, raising the pressure in the hydraulic system to a value slightly lower than the limit value at which the support yields and thus preloading the support.

The manually operated pump 13 may, as shown, be incorporated in the ram and be operated by a handle 14 through a crank 15 and rod 16. The pump 13 delivers oil into the cylinder 1 from the reservoir through the valve 17.

In the form shown in Fig. 2, the prop has a base which provides at its upper end a main hydraulic cylinder 20 and which includes in its lower end a separate cylinder 21 for a high pressure hydraulic accumulator similar to that described with reference to Fig. 1 and including a piston 4' slidable in said cylinder 21 and recessed to form a chamber 6'.

The upper part of the prop is constituted by a hollow ram 22 which operates in the main cylinder 20. This ram has a division plate 23 which forms the base of a fluid reservoir 24.

A skirt 25 of considerable length extends down heneath the division plate 23 and may form a limiting stop for descent of the ram 22.

A relief valve 26, set to relieve at a pressure commensurable with the safe maximum loading of the ram 22 is located in a port leading from the main cylinder 28 through the division plate 23 to the reservoir 24 in the ram.

An auxiliary cylinder 27 of small diameter compared to that of the main cylinder 20 say, one quarter of such diameter, is attached centrally to the bottom plate 28 of the cylinder 20.

A piston 29 operating in the auxiliary cylinder 27 has a tubular connecting rod 39 which passes through glands 31, 32 in the head of the auxiliary cylinder 27 and the division plate 23 respectively.

A much larger piston 33 operating in the hollow ram reservoir space 24 is attached to the upper end of the tubular connecting rod 3%} which is of such length that the large piston 33 is near the head or upper end of the reservoir 24 and the piston 29 in the auxiliary cylinder 27 is near the head of the cylinder 27 when the prop is in the fully closed position. The space 34 above the large piston 33 may normally be vented to atmosphere, but has a connection union 35 for attachment to a pressure air line.

The center of the tubular connecting rod 30 has a passage 36 connecting it to the reservoir 24 beneath the large piston 3c, and the piston 29 in the auxiliary cylinder 27 is drilled to give free passage of fluid from the auxiliary cylinder 27 into the center of the connecting rod 30 and thus between the reservoir 24 and the auxiliary cylinder beneath the piston 29 therein.

A manually operable rotary valve 37 is situated between the hydraulic accumulator and the main cylinder. The valve 37 is rotatable in a casing 50 in the walls of which are provided ports 51, 52 leading to the accumulator 21, ports 53, 54 aligned with ports 55, 56 in the bottom plate 23 and leading to the main cylinder 29 below the ram, 2. port 57 leading to the auxiliary cylinder 27 below the piston 29 and a port 58 in communication with a passage 59 leading to the auxiliary cylinder 27 above the piston 29. The rotary valve 37 is formed with a passage an by which ports 51 and 53 can be connected, a passage 61 by which ports 52 and 58 can be connected, an extending passage 62 by which ports 54 and 57 can be connected and a further longitudinally extending passage 63 by which ports 57 and 58 can be connected. These ports and through passages are so arranged that in difierent positions of the valve (c) the accumulator 21 is isolated and the main cylinder is connected to the auxiliary cylinder 27 below the piston 29 and thus to the reservoir 24 through the tubular rod 34} and the passage 36 (Fig. 5).

(d) the accumulator 21 is connected to the auxiliary cylinder 27 above the piston 29 and the lower end of the auxiliary cylinder 27 is connected to the main cylinder 2t} (Fig. 6).

(e) the reservoir 24 is isolated and the accumulator 21 is connected directly to the main cylinder 26 and the upper and lower ends of the auxiliary cylinder 27 are connected (Fig. 7).

The prop is used as follows: assume that the prop is to be set for the first time and that it has been filled with fiuid and vented. The fluid in the system is completely enclosed and the parts of the prop constitute a closed hydraulic system.

The prop is put in position and the manual valve 37 is set (to position (0) above), as shown in Fig. 5, to put the lower end of the auxiliary cylinder 27 into communication with the main cylinder 20 by way of port 57, passage 62 and ports 54, 56.

Pressure air, say p.s.i. is then connected to the union 35 above the large piston 33 in the reservoir 24.

The pressure thus transmitted to the fluid in the reservoir 24 causes it to flow into and through the tubular connecting rod 30 into the lower end of the auxiliary cylinder 27, through the port 57, through the passage 62 in the manual valve 37 and through ports 54, 56 into the main cylinder 2% thus extending the prop between floor and roof and preloading it with a small pressure. Where facilities exist, it is possible to charge the accumulator initially by compressing the prop in a hydraulic press or the like.

The manual valve is now moved to position (e) (Fig. 7) to shut off the connection between the lower end of the auxiliary cylinder 27 and the main cylinder 20 and to connect the latter (20) to the cylinder of the hydraulic accumulator 21 by way of ports 55, 53, passage 60 and port 51 and also to connect the lower and upper ends of the auxiliary cylinder 27 by way of port 57, passage 63, port 58 and passage 59..

As the roof subsides, fluid pressure is set up in the main cylinder 20 and fluid passes through the passage 60 in the valve 37 to the accumulator 21 until it is fully charged. Thereafter, further increase of roof pressure causes the relief valve 26 in the division plate 23 to open and pass fluid from the main cylinder 20 to the reservoir 24. The passage of fluid from the main cylinder to the reservoir causes the large piston 33 to rise. This motion is transmitted to the piston 29 in the auxiliary cylinder 27 and fiuid passes from above this piston, through the passage 59, port 58 and passage 63 in the valve 37 to the lower end of the auxiliary cylinder through port 57 and up through the tubular connecting rod 30 to the reservoir 24.

The process of pressure relief continues so long as the prop is in position and roof subsidence continues and it will be appreciated that the hydraulic reservoir constantly acts to restore any too sudden pressure drop in the main cylinder 20 caused by hysteresis in the relief valve spring.

When the prop is to be withdrawn the valve is again set to position (0), Fig. 5, to isolate the hydraulic accumulator cylinder 21 from the main cylinder 20 and to connect the lower end of the auxiliary cylinder 27 to the main cylinder. The ram 22 now descends forcing fluid from the main cylinder 20 through ports 56, 54, passage 62 and port 57 into the lower end of the auxiliary cylinder 27 and through the tubular connecting rod 30 into the reservoir 24.

When the prop is to be re-set there is no need to employ pressure air once the hydraulic accumulator has been initially charged.

The prop is placed in its new location and the manually operated valve is set in position (d) (Fig. 6) to admit high pressure fluid from the accumulator 21 through port 52, passage 61, port 58 and passage 59 solely to the upper end of the auxiliary cylinder 27 and to connect the lower end of the auxiliary cylinder 27 with the main cylinder 20 by way of port 57, passage 62, and ports 54, 56.

A downward force is thus transmitted to the large piston 33 in the reservoir 24 and fluid is forced through the tubular connecting rod 30 into the lower end of the auxiliary cylinder by way of port 57 and passage 62, through the valve 37 and into the main cylinder 20 through ports 54, 56. The fluid pressure thus admitted to the main cylinder acts on the dilferential area of the ram 22 (the area of the depending skirt 25) and extends the prop against the roof.

The manually operated valve 37 is now set once more to position (e), Fig. 7, to shut off the lower end of the auxiliary cylinder 27 from the main cylinder 20, to connect the upper end of the auxiliary cylinder 27 to the reservoir through the lower end of the auxiliary cylinder 27 and to connect the hydraulic accumulator cylinder to the main cylinder 20.

The high pressure fluid from the hydraulic accumulator, acting now on the full area of the ram 22, presets the prop to a high proportion of its full load capacity.

It will be appreciated that this form of prop is unaffected by the angle at which it is set or by the exact quantity of oil within the system. The prop would operate even if completely inverted.

It will be understood that there are several other arrangements by which the yielding of a roof support under pressure in one setting can be employed to charge an hydraulic accumulator or other energy storing device, and the invention is not therefore restricted to the details of the preferred forms described which may be modified without departing from the broad ideas underlying them.

I claim:

1. A roof support for a mine, comprising a cylinder, a hydraulic ram movable in said cylinder, a hydraulic accumulator connected to said cylinder, valve means controlling the connection between said accumulator and cylinder to selectively confine the pressure in the accumulator and release pressure in said cylinder independently of the accumulator, and means connected to said accumulator for withdrawing energy stored in the accumulator and applying the withdrawn energy to do useful work.

2. A roof support for mines, comprising a closed bydraulic system including a main cylinder, a ram movable axially in said cylinder for extending the support, a hydraulic accumulator in communication with said cylinder and charged by axial compression of the ram in the cylinder, and a manually controlled valve having means independent of the accumulator for retracting said ram, and means controlling communication between said cylinder and accumulator to release the energy stored and to extend and preload the support.

3. A roof support for mines including relatively movable parts affected by subsidence of the mine roof when the support is in position, an energy storing device charged by relative movement between said parts, means operatively associated with said parts selectively permitting relative movement therebetween independent of said energy storing device, and means for selectively releasing the energy in said storing device independent of said movable parts for performing useful work.

4. A roof support according to claim 2, wherein said ram is hollow and constitutes a fluid reservoir with the main cylinder, an auxiliary cylinder in said support, said valve selectively connecting said auxiliary cylinder with the accumulator for raising the ram into contact with the roof for setting the support and with the main cylinder once the support is set to exert a preloading pressure on the ram.

5. A roof support according to claim 4 in which each cylinder is provided with a piston, means interconnecting said pistons, said valve connecting said accumulator with the main cylinder to exert pressure on the piston therein and through said interconnecting means to the piston in the auxiliary cylinder to put pressure upon the fluid in said reservoir and thus to transfer it to the main cylinder.

6. A roof support according to claim 5 including a third cylinder having a piston working therein, and means selectively connecting said accumulator to either side of the last mentioned piston and to a conveyor for moving the conveyor relatively to the support.

References Cited in the file of this patent UNITED STATES PATENTS 1,752,101 Meutsch Mar. 25, 1930 1,812,577 Albertine June 30, 1931 1,903,887 Widener Apr. 18, 1933 1,964,003 McBride June 26, 1934 1,976,129 Johnson Oct. 9, 1934 2,136,080 Joy Nov. 8, 1938 2,165,095 Frechette July 4, 1939 2,407,796 Page Sept. 17, 1946 2,490,284 Simart Dec. 6, 1949 2,584,820 Steinhotf Feb. 5, 1952 2,621,631 Dowty Dec. 16, 1952 2,711,634 Joy June 28, 1955 FOREIGN PATENTS 493,811 Belgium Feb. 28, 1950 623,945 Germany Jan. 8, 1936 810,863 Germany Aug. 13, 1951 

